Carbon Capture and Storage (CCS)

• CCS Overview
• Carbon Dioxide Separation and Capture
• Geological Storage of Carbon Dioxide

Overview

Carbon capture and storage (sequestration) is one of the most promising ways for reducing the buildup of greenhouse gases in the atmosphere.

Even under the most optimistic scenarios for energy efficiency gains and the greater use of low or no-carbon fuels, carbon capture and storage will likely be essential if the world is to stabilise atmospheric concentrations of greenhouse gases at acceptable levels.

What is carbon sequestration?

Carbon sequestration is the capture and storage of carbon dioxide (CO2) that would otherwise be emitted to the atmosphere. CO2 can be captured at the point of emission (or point source), or removed from the air in the process of photosynthesis. The captured gases can be stored in underground reservoirs, converted to rock-like solid materials, or absorbed by trees, grasses, soils, or algae.

How is carbon separated and captured?

Before CO2 from power plants can be stored, it must first be captured as a relatively pure gas. Essentially the capture of the CO2 can be done at either the pre-combustion or post-combustion stage, as summarised below:

• Pre-combustion Capture: Here coal is gasified to form a mixture of hydrogen and CO2, called synthesis gas or "syngas," and CO2 is captured from the syngas before it is combusted.

This process is central to IGCC (Integrated Gasification Combined Cycle) power plants.

• Post-combustion Capture (PCC): This involves capturing CO2 from the power station flue gas after fuel has been combusted in air.

• Oxy-Fuel combustion: A refinement of the PCC approach above involves the combustion of pulverised coal in a mixture of oxygen and recirculated flue gas in order to reduce the net volume of flue gases from the process and to substantially increase the concentration of carbon dioxide (CO2) in the flue gases – compared to the normal pulverised coal combustion in air. Oxy-Fuel combustion offers a low risk step development of existing pf power generation technology to facilitate CO2 capture and storage.

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